Cut the ham into pieces. Bring the beef bouillon to a boil and add the cooked ham. Let simmer for 1 minute. Cover and let cool. Sieve. Season to taste. Reduce the white wine to 20 ml. Add the sherry, chicken bouillon, grated cheese and the cornstarch. Heat, while stirring into a homogeneous mixture. Let boil. Allow to cool.Spray the cheese sauce on toast and warm under the grill. Clean the mushrooms and fry in hot butter. Season to taste.